1. Field of Invention
The present invention relates to an electronic circuit. More particularly, the present invention relates to a functional device and a test mode activation circuit of the same.
2. Description of Related Art
Typically, a semiconductor integrated circuit (IC) device incorporates a test mode activation circuit for generating a test mode activation signal. The test mode activation signal puts the IC device in a test mode for testing functional circuits in the IC device. In a conventional design, the test mode activation signal is a control voltage higher or lower than a predetermined level. Once the IC device detects the control voltage, the IC device switches from the operation mode to the test mode.
However, the IC device may be accidentally put in the test mode by a noise signal, such as a ground noise applied to the input of the test mode activation signal. On the other hand, if the voltage level of the control voltage is higher than the highest tolerable voltage of the components in the IC device, the components in the IC device may be damaged.
Accordingly, what is needed is a functional device and a test mode activation circuit of the same to address the issues mentioned above.